<template>
  <div class="SidebarRedFang">
    <el-checkbox
      :indeterminate="isIndeterminate"
      v-model="checkAll"
      @change="handleCheckAllChange"
      >弹道</el-checkbox
    >
    <div style="margin: 15px 0"></div>
    <el-checkbox-group
      v-model="checkedCities"
      @change="handleCheckedCitiesChange"
    >
      <div class="myFlex">
        <el-checkbox v-for="city in cities" :label="city" :key="city">{{
          city
        }}</el-checkbox>
      </div>
    </el-checkbox-group>
  </div>
</template>

<script>
const cityOptions = ["上海", "北京", "广州", "深圳"];
export default {
  data() {
    return {
      checkAll: false,
      checkedCities: ["上海", "北京", "广州", "深圳"],
      cities: cityOptions,
      isIndeterminate: true,
    };
  },
  watch: {
    checkedCities: {
      immediate: true,
      handler(val) {
        this.$emit("CheckedData", val);

        // alert(val)
      },
    },
  },

  mounted() {
    //1、首先请求左侧列表接口
    //  1.全选赋值checked:[]
    //2、监听checked变化请求接口
  },

  methods: {
    handleCheckAllChange(val) {
      this.checkedCities = val ? cityOptions : [];
      this.isIndeterminate = false;
    },
    handleCheckedCitiesChange(value) {
      let checkedCount = value.length;
      this.checkAll = checkedCount === this.cities.length;
      this.isIndeterminate =
        checkedCount > 0 && checkedCount < this.cities.length;
    },
  },
};
</script>

<style lang="less" scoped>
.SidebarRedFang {
  .myFlex {
    display: flex;
    flex-direction: column;
  }
}
</style>